Thylacosmilinae

Thylacosmilinae is an extinct subfamily of saber-toothed predatory marsupials that lived in South America during the Late Miocene and Pliocene epochs. These animals are characterized by their extraordinarily long, saber-like canine teeth, which were not rooted as in placental saber-toothed cats but rather grew continuously throughout the animal's life. The subfamily contains only one genus, Thylacosmilus, and one known species, Thylacosmilus atrox.

Thylacosmilus was a medium-sized predator, roughly the size of a jaguar. Its most striking feature was its saber teeth, which could be up to 15 centimeters long and extended well below the lower jaw. These teeth were likely used for delivering killing bites to prey, possibly by slashing the throat or belly. The skull of Thylacosmilus was robust, with a deep lower jaw that protected the saber teeth and neck vertebrae that may have supported them.

The diet of Thylacosmilus is not definitively known, but it is presumed to have preyed on the large herbivores of South America, such as ungulates like toxodonts and macrauchenias. The adaptation of saber teeth suggests a specialized predatory strategy. The extinction of Thylacosmilinae coincided with significant environmental changes in South America and the eventual interchange of fauna with North America.